1. Field of the Invention
The present invention relates generally to valve systems and, in a particular embodiment, to apparatus and methods for a compact subsea valve system that is highly suitable for deep water installations wherein installation dimensions are limited.
2. Description of the Background
Remote subsea gate valves and fail-safe gate valves are typically controlled with hydraulic actuators and may comprise a lower riser package. The hydraulic actuators and often their controls may be located on or near the ocean floor along with other equipment. Due to the cost and limited space when positioning equipment on the ocean floor, it is highly desirable that any equipment be as compact as possible while still affording excellent reliability and simplified maintenance procedures. Thus, the valve equipment must typically fit within a relatively small frame, with limited subsea valve installation dimensions, that may be lowered to the sea floor for subsea operation.
In case hydraulic power is lost for some reason, a manual override control may be necessary for valve operation. The potential for loss of hydraulic power is also met by providing a fail-safe hydraulic actuator which moves the gate valve to a preselected position should hydraulic power fail. While manual override controls, hydraulic actuators, and fail-safe hydraulic actuators are commonly utilized in subsea installations, such devices further increase the size of the valve assemblies. My previous U.S. patent application Ser. No. 09/802,209, filed Mar. 8, 2001, and incorporated herein by reference, discloses an exemplary hydraulic fail-safe actuator and manual override control having significantly reduced dimensions that may be used in an underwater installation in accord with the present invention. In this application, even further unique improvements are disclosed for yet more substantial reductions in overall subsea valve system dimensions.
Manual override controls may be manually operated by divers or by remotely controlled underwater vehicles (ROVS) and are commonly operated in a standard manner. Thus, any operation of valves by divers or ROVS to override the use of the standard hydraulic valve actuators is considered manual operation of the valve for purposes of the present invention. Typically, such operation involves rotation of a shaft or wheel. In accord with the present invention, it is desirable that even highly compact valve systems as taught herein, including corresponding manual override controls, may be operated according to standard operating procedures to avoid the need to operate different manual override controls in different ways and so thereby avoid confusion.
Previously available deepwater valve installations tend to have numerous limitations including bulky dimensions. Consequently, there remains a need for a compact subsea valve system that offers dependable operation at deep water depths, reduces the size of the overall subsea valve system, provides manual override controls which may be utilized in conjunction with both fail-safe actuators and other types of hydraulic actuators, and significantly increases valve system configuration flexibility. Those skilled in the art have long sought and will appreciate the present invention which addresses these and other problems.
The present invention is embodied in a design for a subsea gate valve system and method that allows more reliable and improved operation within reduced installation dimensions for any practical water depth, e.g., 10,000 feet.
Thus the present invention provides for a subsea gate valve assembly which may comprise one or more elements such as, for instance, a gate valve housing, a gate element moveably mounted within the gate valve housing, the gate element having a first side and a second side, a valve operating stem connected with respect to the first side of the gate element, a hydraulic actuator housing secured with respect to the gate valve housing, a hydraulically activated element mounted within the hydraulic actuator housing and operatively connected with the operating stem for moving the valve operating stem and the gate element between a first position and a second position, a balance stem secured with respect to the second side of the gate element, a manual override housing secured with respect to the gate valve housing, and/or a manually activated member mounted within the manual override housing and operatively connected to the balance stem for moving the gate element between the first position and the second position.
In one embodiment, the manually activated member within the manual override housing comprises a threaded portion, the threaded portion may comprise reverse cut threads. The subsea valve may further comprise a second moveable element mounted within the manual override housing having a second threaded portion wherein the second portion may comprise reverse cut threads and the first threaded portion engages the second threaded portion.
Preferably, at least one of the manually activated members or the second moveable element is rotatable. The subsea valve assembly may further comprise a rib for interconnection with the manual override housing and for engaging at least one of the manually activated member or the second moveable element to prevent rotation with respect to the manual override housing. The manually activated member within the manual override housing may further comprise an override drive shaft wherein the override drive shaft is rotatably mounted within the manual override housing. In one embodiment, an override slave member has a second threaded portion and is slidably mounted within the manual override housing to thereby move longitudinally in response to rotation of the override drive shaft.
The gate valve housing may further comprise a valve body, a first gate valve bonnet secured to the valve bonnet wherein the hydraulic actuator housing may be secured to the first gate valve bonnet, and a second gate valve bonnet secured to the valve body wherein the manual override housing may be secured to the second gate valve bonnet.
The valve body may have a first side and a second side. In one embodiment, the first gate valve bonnet may be attachable to the first side or the second side and the second gate valve bonnet may be attachable to the first side or the second side.
A manual override control for a subsea valve assembly may comprise a manual override housing, a manual override drive shaft rotatably mounted within the manual override housing, the manual override drive shaft having a first threaded portion, the first threaded portion may comprise left-handed threads wherein a manual override slave member operatively connected to the manual override drive shaft and the gate.
Preferably, the manual override slave member has a second threaded portion with left-handed threads engageable with the first portion such that the gate is translationally moveable between the first position and the second position in response to rotation of the manual override drive shaft.
The manual override control may further comprise at least one rib and at least one slot defined between the slave member and the manual override housing wherein the at least one slot receives the at least one rib to thereby permit translational movement of the slave member with respect to the manual override housing and to thereby prevent rotational movement of the slave member with respect to the manual override housing. In one embodiment, the rib is affixed to the manual override housing and the slot is defined within the slave member.
Moreover, the manual override control may further comprise a rotational connection between the manual override drive shaft and the manual override housing such that the rotational connection permits rotational movement of the manual override drive shaft with respect to the manual override housing and prevents translational movement of the manual override drive shaft with respect to the manual override housing.
Thus, the present invention provides a method for assembling a gate valve assembly which method may comprise one or more steps such as, for instance, inserting a gate valve into a gate valve housing, attaching an operating stem to the gate valve, attaching a balance stem to the gate valve, connecting a hydraulic operator to the operating stem, and/or connecting a manual override operator to the balance stem. If desired, the hydraulic operator may be a hydraulic fail-safe actuator or may be another type of hydraulic actuator. The method may further comprise providing a manual override housing for the manual override operator, and/or attaching the manual override housing to the gate valve housing. Additional steps may include providing a first left-handed threaded portion on a rotatable member and/or mounting the rotatable member within the manual override housing. Yet additional steps may comprise mounting a slave member for translational movement within the manual override housing, providing a second left-handed threaded portion on the slave member, engaging the first left-handed threaded portion with the second left-handed thread portion, and/or interconnecting the balance stem to the slave member.
Additionally, the method may comprise forming the gate valve housing by attaching a first gate valve bonnet to a first side of a gate valve body, and/or attaching a second gate valve bonnet to a second side of the gate valve body. Other assembly steps may comprise attaching the hydraulic operator to the first gate valve bonnet, attaching the manual override operator to the second gate valve bonnet, extending the operating stem through the first gate valve bonnet, and/or extending the balance stem through the second gate valve bonnet.
In one preferred embodiment, the method comprises providing that the first side of the gate valve body and the second side of the gate valve body are substantially symmetrical such that the first gate valve bonnet is selectively connectable to the first side of the gate valve body or the second side of the gate valve body.
A method for assembly a manual override control for a subsea valve actuator assembly is also provided and may comprise providing a manual override drive shaft with a threaded portion having left-handed threaded portion, rotatably mounting the manual override drive shaft within a manual override housing, mounting a connector element within the manual override housing for connecting with the gate, and/or mounting the override drive shaft with respect to the connector element such that rotational movement of the drive shaft results in translational movement of the connector element. The method may further comprise providing the connector element with a threaded portion for engaging the left-handed threaded portion of the drive shaft, and/or affixing a rotational connection to the manual override housing, and/or interconnecting the manual override drive shaft to the rotational connection such that the manual override drive shaft is rotatable with respect to the manual override housing but is prevented from rotational movement with respect thereto.
In one embodiment, a subsea gate valve assembly may comprise a gate valve housing with a first gate valve housing side and a second gate valve housing side opposite to the first gate valve housing side, a gate element moveably mounted within the gate valve housing for movement between a first position and a second position, a hydraulic actuator housing mounted to the first gate valve housing side, a hydraulically activated element mounted within the hydraulic actuator housing and operatively connected to the gate element for moving the gate element between the first position and a second position, a manual override housing mounted to the second gate valve housing side, and a manually activated member mounted within the manual override housing and operatively connected to the gate element for moving the gate element between the first position and the second position.
It is an object of the present invention to provide an improved subsea valve system and method.
It is another object of the present invention to provide a subsea valve system with a more compact configuration.
An advantage of the present invention is the significant size (height and weight) reduction achieved by a design in accord with the invention.
Another advantage of the present invention is increased flexibility in valve system configuration.
These and other objects, features, and advantages of the present invention will become apparent from the drawings, the descriptions given herein, and the appended claims.
The FIGURE is an elevational view, partially in section, of a subsea valve assembly in accord with the present invention.
While the present invention will be described in connection with presently preferred embodiments, it will be understood that it is not intended to limit the invention to those embodiments. On the contrary, it is intended to cover all alternatives, modifications, and equivalents included within the spirit of the invention and as defined in the appended claims.